I think it's a number that shifts as you get older. I'm not sure how far it shifts, and IMO it would be odd to see it shift past eighteen, but maybe that's just me being a bit young. Right now I definitely don't think I'd call anything after around 13 as something I grew up with, but as my teens as a whole shift far enough into the past I definitely think my view on that could change, and I wouldn't find it horribly odd for someone enough older than me to call something they discovered around sixteen something they grew up with.